It is common practice that when a business, whether small or large decided to do an IT project, the first thing a project manager will do is to unplug the Gantt chart and start planning including budgeting, time and hope.
It is then presented to the board (the big business), or the owners (in small businesses) for approval. Then everything has to work according to plan, with some minor adjustments accounted for in the plan. To know more about risk mitigation you can also visit https://www.crowdbridge.ca/.
It is common that every large or small business carries risks. The larger the project is, the greater the risk and the stock will be higher. This risk may eventually heavy business costs in terms of monetary loss or damaged reputation.
Another common thing that happens when a project has first submitted the assumptions. While it is easy to make assumptions, the problem is that some may appear true until someone actually doing the work and found it otherwise.
Testing is also very important. Testing should be done widely even after little minute changes. Therefore, the best practice is to do a lockdown release (i.e. no small change again, a quick repair, etc.), and thoroughly test release.
Stakeholders should be made to understand that even small changes may seem innocent and free of risk, the fact is, no one can give a 100% guarantee that it is. Stakeholders should be made to understand that any quick fixes that will cancel previous long test and re-test the pain-staking required.